This invention relates to movement and control of objects and more particularly to micro positioning devices and a method which can be used in parallel precision assembly or parts feeding. Further, this invention is directed to micro manipulation of objects using a friction force field. The manipulation and positioning method is described in a publication entitled Micromanipulation Using a Friction Force Field, published in the proceedings of 20001 IEEE, International Conference on Robotics and Automation, Seoul, Korea, May 21-26, 2001, which is incorporated herein by reference.
The current lack of manufacturing techniques for very high volume handling of small objects presents a technology barrier to commercial success in various fields of micro systems technology (MST) such as micro electromechanical systems (MEMS). A fundamentally new approach to automated massive parallel manipulation of small-sized objects or parts is needed and is provided by this invention.
Mass production of miniature components such as integrated circuits, micro electromechanical systems (MEMS), and the like, requires fundamental innovations in parts handling. Components of such systems are built using micro fabrication processes derived from VLSI technology, which allows the manufacture and handling of thousand or millions of components in parallel. The active surface device disclosed herein uses a new approach to automated object manipulation. Instead of handling a single object directly, for example, with a robot gripper, an active surface device, such as a pneumatic surface device can be used to manipulate multiple objects simultaneously. Such an automation device permits parallel and distributed, sensing and actuation, and is particularly attractive for handling batch micro fabricated objects, the large numbers and small dimensions of which preclude conventional pick and place operations with robot grippers. Accordingly, there is a particular need for methods and equipment to provide such capability.
Micro assembly, which involves high-precision handling and assembly of objects, is an important technology. Among the various micro assembly techniques, assembly using a positioning device is a conventional and reliable approach. In that approach, the fine resolution of the positioning device is a critical requirement for an object""s successful manipulation and assembly.
Commercial positioning systems now provide high resolution and repeatability. There are conventional XY positioning tables, articulate joint robots, and some parallel mechanisms. Prototype systems have been described which use stepping motors and inertial drives to obtain sub-micrometer motion resolution. It has been generally observed that handling of smaller parts requires larger machines. Also there are actuator arrays, which usually consist of a regular grid of motion pixels that can generate force or motion in a specific direction. The actuation can be provided by a variety of methods such as electrostatic forces, air jets, thermo-bimorph or magnetic actuation.
Illustrative precision positioning devices of the prior art include U.S. Pat. No. 5,351,412 which describes a pair of aluminum electrodes on a piezoelectric element bonded on a silicon wafer. Voltages were applied to the aluminum electrodes and phase difference causes vertical motion of PZT which make rotational and horizontal motion of electrode pin. U.S. Pat. No. 6,008,610 describes a high position control apparatus for fine stages carried by coarse stage. By adjusting the fine stages, any synchronous errors between the fine stages during scanning may be dynamically corrected. U.S. Pat. No. 5,994,820 discloses an electromechanical positioning unit formed as an inertial drive to position objects with atomic scale positioning precision and with displacement ranges up to centimeters. In U.S. Pat. No. 5,978,172, a voice coil driven positioning device is provided for positioning the magnetic head of a tape drive relative to the tape of a removable tape cartridge.
Piezoelectric (PZT) actuators can be used for precision manipulation with enhanced range in this invention. They have an outstanding resolution and fast response, therefore these actuators have been used in many applications such as the optical alignment process, biomedical object manipulation, and miniature robotics. A main drawback of the PZT actuator is its limited working distance. Since a PZT actuator can currently generate a maximum of about 0.1 about % strain, the usual working distance ranges from about 10 to about 100 microns (micrometer). This is generally too short a distance for the flexible manipulation of an object. If the positioning device could provide a relatively large working range that allowed flexible handing of the micro-object as well as fine resolution within a miniaturized physical scale, it would be very attractive for flexible micro-object handling.
In addition, current demand in the manufacturing of microsystem devices requires reduced cost and reduced cycle time. Serialized manipulation and assembly processes are inefficient in providing the required throughput, so parallel processes are highly preferred. The conventional manipulation scheme is difficult to adapt to parallel processing because of its physical dimension, which is generally much bigger than the components being handled. If a positioning device can provide the capability to manipulate multiple objects within a relatively small physical dimension along with a cost-effective configuration, it will have a great advantage over the more traditional serialized assembly process.
The present invention provides mechanisms and methods for using piezoelectric actuators for multi-object manipulation with an enhanced working range and degrees of freedom while maintaining the inherent fine resolution of the actuator. Positioning of multiple objects is carried out simultaneously by shared actuators. The device consists of two piezoelectric actuators driven for linear motion in X and Y directions, and a two dimensional array of object-holding heads, which can apply force such as pneumatic suction force to the objects being manipulated. The two actuators move the object-holding heads as required.
The present invention addresses the need for high accuracy combined with a reasonable large dynamic range, parallel processing, and low system cost through the use of a few actuators.
The present invention is directed to an active surface device for manipulation and positioning of an object on a surface, comprising a surface on which to support an object, at least one movable gripper means at the surface to grip the object and move the object to another position on the surface, means to release the object from the grip of the movable griper, fixed gripper means at the surface to, including means to grip the object and restrain movement of the object during movement of the movable gripper means to a position for further movement of the object, a pair of actuator means, individually adapted to move the movable gripper means in X and Y directions.
The term xe2x80x9cactive surfacexe2x80x9d as used herein means a surface comprising means for gripping, holding and, moving an object about on the surface. An active surface device includes such a surface and all of the necessary components to accomplish movement of an object on the surface.
The basic principles of the invention are described herein. In general for convenience, the description is given in terms of a suction force being used to hold the object on the movable or fixed holding heads. For motion in a given direction, e.g. the x-direction, there are two sets of grippers or object-holding heads that can hold onto an object on a flat surface. One set is fixed relative to the surface on which the object is to be moved or positioned. The other set can be moved by an actuator such as a piezoelectric actuator relative to this surface, this set is used to move the object step by step.